JAKARTA - The National Transportation Safety Committee (NTSC) released a preliminary report on the condition of the Sriwijaya Air SJ-182 aircraft from the analysis of the black box flight data recorder (FDR) data.
The head of the NTSC Aviation Accident Investigation Subcommittee, Nurcahyo Utomo, admitted that he found the autothrottle had an anomaly before the plane crashed.
Autothrottle is a gas regulating system so that the pilot regulates the speed and thrust of the aircraft automatically within safe limits.
"The authrottle is experiencing an anomaly. The left plane's engine is retreating too far. Meanwhile, the right one is completely motionless, like a jam," Nurcahyo Utomo said in a virtual press conference, Wednesday, February 10.
However, Nurcahyo admitted that he did not know whether the left or right side of the aircraft engine was damaged, if he saw the results of the investigation from the FDR black box or the recording of flight data.
"So, we don't really know what is damaged on the left or right because both of them show different attitudes. This is what we have not been able to explain to this day whether there is autothrottle damage," he said.
Nurcahyo said, the cause of the autothrottle experiencing anomaly is not yet known because the autothrottle gets input from 13 other components. "Hopefully we can answer with several components that we send for further research," he said.
As for the chronology of flight data prior to the crash, Sriwijaya Air SJ-182 initially departed Jakarta Soekarno-Hatta International Airport with the aim of Pontianak Supadio Airport at 14:36 WIB, Saturday, January 9, 2021.
After take off, this aircraft follows the departure path that has been determined following the ABASA 2D departure path. FDR noted that when at an altitude of 1,980 feet, the autopilot began to activate.
"Then, the plane continues to rise. At an altitude of approximately 8,150 feet, the left engine power control lever (throttle) moves backward and the engine power or engine speed also decreases. Meanwhile, the right side engine is fixed," said Nurcahyo in a virtual press conference. , Wednesday, February 10.
Furthermore, at 14:38 WIB, 51 seconds, the Sriwijaya Air SJ-182 pilot asked the air traffic control (ATC) to turn towards 75 degrees due to weather conditions. ATC allows.
Due to a change in direction, ATC estimates that Sriwijaya Air SJ-182 will meet another plane departing from Soekarno-Hatta on the south runway.
Although Sriwijaya Air SJ-182 departed from the northern runway, these two planes had the same destination, namely Pontianak.
"Because it was expected to pass, SJ-182 was asked to stop climbing at an altitude of 11,000 feet," he said.
At 14:39 WIB, 47 seconds, the plane passed an altitude of 10,600 feet, the plane was in the direction of 46 degrees and began to look to turn left. The left engine power control lever moves backwards again, while the right one is still.
Then, ATC gave instructions to the SJ-182 pilots to ascend to an altitude of 13,000 feet. The pilot answered at 14:39 WIB, 59 seconds. "This is the last communication recorded on the pilot's communication recording with ATC at Soekarno Hatta Airport," said Nurcahyo.
At 14:40 WIB, 05 seconds, FDR recorded the highest altitude of the aircraft at 10,900 feet. After this altitude, the plane began to descend. The autopilot is suddenly inactive. The plane's direction at that time was 16 degrees.
At that time, the nose of the Sriwijaya Air SJ-182 aircraft was in an up or pitch up position and the plane began to tilt to the left. The left engine power regulating lever is reduced again, while the right one remains.
At 14:40 WIB, 10 seconds, FDR recorded the system so that the pilot set the speed and thrust of the aircraft automatically (autothrottle) was not active. Then, the stance of the plane lowered. 20 seconds later, FDR stops recording.
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